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Author Topic: Does electricity ''weaken'' when it is being ''stretched''?  (Read 2744 times)

Offline Thebox

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If I could electrocute myself without dying, attached to the source of electricity such has a bare wire, by my finger, if I slowly withdrew my finger does the electricity stretch and weaken before eventually the circuit is broken?


« Last Edit: 17/12/2015 15:46:42 by chris »


 

Offline Thebox

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The reason I ask is because of this.



 

Offline alancalverd

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Never mind the diagram. As the contact area decreases, so the resistance of the contact increases so the current though your body will decrease according to Ohm's Law

I = V/R

If the voltage was high enough to sustain an arc as you withdrew your finger, the arc might indeed appear to "stretch" and I will decrease, but the decrease won't be linear: as any electrical engineer will tell you "them arcs is funny things" - which is why nobody has made a decent fusion reactor - plasma physics gets more complicated the closer you look at it!
 

Offline wolfekeeper

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The term 'electrocute' comes from 'execute' and 'electricity'. So it means, die by electricity. So, by definition, you can't electrocute yourself without dying.

Anyway, back to the problem. The arc resistance will be very low, and not depend that much on distance; it won't weaken; but it will suddenly stop. You pretty much either have an arc or you don't.
 

Offline Thebox

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The term 'electrocute' comes from 'execute' and 'electricity'. So it means, die by electricity. So, by definition, you can't electrocute yourself without dying.

Anyway, back to the problem. The arc resistance will be very low, and not depend that much on distance; it won't weaken; but it will suddenly stop. You pretty much either have an arc or you don't.

Thank you, to confirm the definition of arc you are meaning is this -'' a luminous electrical discharge between two electrodes or other points''?
 

Offline Thebox

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Never mind the diagram. As the contact area decreases, so the resistance of the contact increases so the current though your body will decrease according to Ohm's Law

I = V/R

If the voltage was high enough to sustain an arc as you withdrew your finger, the arc might indeed appear to "stretch" and I will decrease, but the decrease won't be linear: as any electrical engineer will tell you "them arcs is funny things" - which is why nobody has made a decent fusion reactor - plasma physics gets more complicated the closer you look at it!

Thank you , and what spectral colour would this arc be?
 

Offline Colin2B

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You pretty much either have an arc or you don't.
You are also pretty much dead or you're not.
So Mr Box, listen to Wolfkeeper, don't muck about with the electricity, your diagrams won't help!
Interestingly it is current that kills, not voltage, and the current doesn't need to be very high.

Thank you , and what spectral colour would this arc be?
Blue end of white.
 
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Offline evan_au

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Quote from: TheBox
to confirm the definition of arc you are meaning is this -'' a luminous electrical discharge between two electrodes or other points''?
Yes.

Quote
what spectral colour would this arc be?
It has a lot of ultraviolet, as electrons are ripped right off the atoms in the center of the arc, and they recombine outside the central region, producing UV.

Quote from: Colin2B
the current doesn't need to be very high
30mA of AC is generally considered potentially lethal, if it passes by your heart (eg from hand to hand). Residual Current circuit breakers are designed to cut off the current very quickly (about 200ms) if the current exceeds 30mA. 
 

Offline Thebox

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Quote from: TheBox
to confirm the definition of arc you are meaning is this -'' a luminous electrical discharge between two electrodes or other points''?
Yes.

Quote
what spectral colour would this arc be?
It has a lot of ultraviolet, as electrons are ripped right off the atoms in the center of the arc, and they recombine outside the central region, producing UV.

Quote from: Colin2B
the current doesn't need to be very high
30mA of AC is generally considered potentially lethal, if it passes by your heart (eg from hand to hand). Residual Current circuit breakers are designed to cut off the current very quickly (about 200ms) if the current exceeds 30mA.


Thank you Evan I do understand it is amps that kill and not voltage, my first ever job many years ago was for a company that sold electrical installation components such as R.C.B's.

Does electricity ''red shift'' at all when being ''stretched''?
 

Offline Thebox

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You pretty much either have an arc or you don't.
You are also pretty much dead or you're not.
So Mr Box, listen to Wolfkeeper, don't muck about with the electricity, your diagrams won't help!
Interestingly it is current that kills, not voltage, and the current doesn't need to be very high.

Thank you , and what spectral colour would this arc be?
Blue end of white.


Thanks Colin, I do know not to mess with electricity, I am not Tesla lol and I would not have the mechanical ability or components to build any devices, although I could probably ''bodge'' something together lol, Mcgiver style lol.
In the past I have held a h.t lead or several just for kicks. When a spark plugs spark is orange and not blue, is that a poor contact or the gap in the spark plug too big? 
or something else such as magnitude/timing decrease?
« Last Edit: 18/12/2015 09:43:31 by Thebox »
 

Offline Colin2B

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Re: Does electricity ''weaken'' when it is being ''stretched''?
« Reply #10 on: 18/12/2015 09:54:18 »
Does electricity ''red shift'' at all when being ''stretched''?
No, because it isn't being stretched.
What you are creating is a mini lightning bolt.
The electricity ionises the air in the gap which creates the light, but it is of a very wide spectrum. As Evan says it contains a lot of UV (which is why you should never look at a welder's arc) but it also has a lot of radio frequencies in it. You have probably heard lightning interfere with the radio, early radio transmitters were based on a spark gap.
 
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Offline Thebox

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Re: Does electricity ''weaken'' when it is being ''stretched''?
« Reply #11 on: 18/12/2015 09:58:19 »
Does electricity ''red shift'' at all when being ''stretched''?
No, because it isn't being stretched.
What you are creating is a mini lightning bolt.
The electricity ionises the air in the gap which creates the light, but it is of a very wide spectrum. As Evan says it contains a lot of UV (which is why you should never look at a welder's arc) but it also has a lot of radio frequencies in it. You have probably heard lightning interfere with the radio, early radio transmitters were based on a spark gap.

Thank you Colin, I am aware of ''arc eye'' from welding flash.

Light bulbs , why do they not ''lightning'' to the ground, is it the glass that stops the electricity finding earth or the distance?

 

Offline Colin2B

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Re: Does electricity ''weaken'' when it is being ''stretched''?
« Reply #12 on: 18/12/2015 12:12:06 »
Light bulbs , why do they not ''lightning'' to the ground, is it the glass that stops the electricity finding earth or the distance?
yes, the glass acts as an insulator but also the bulb is filled with an inert gas or a vacuum which doesnt ionise. However, even if the filament was open to the air mains voltage isnt high enough to jump the distance to ground from a light fitting.
Not bad, you got 2 of them  :)
 

Offline Thebox

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Re: Does electricity ''weaken'' when it is being ''stretched''?
« Reply #13 on: 18/12/2015 15:52:47 »
Light bulbs , why do they not ''lightning'' to the ground, is it the glass that stops the electricity finding earth or the distance?
yes, the glass acts as an insulator but also the bulb is filled with an inert gas or a vacuum which doesnt ionise. However, even if the filament was open to the air mains voltage isnt high enough to jump the distance to ground from a light fitting.
Not bad, you got 2 of them  :)

Thank you, so if we had an exposed element, with no insulator, that the nearest earth was to far away to create an arc, does the electricity still escape into the atmosphere or ''draws'' off towards the earth?


and what in the ground of the earth would draw electricity to it, if the element was close enough and exposed?

« Last Edit: 18/12/2015 15:57:27 by Thebox »
 

Offline alancalverd

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Re: Does electricity ''weaken'' when it is being ''stretched''?
« Reply #14 on: 18/12/2015 23:16:20 »
The resistance of the lamp filament (around 1000 ohm) is much lower than that of the air path to the ground (at least 1,000,000,000 ohms for dry air) so nearly all the current flows from the live to the neutral conductor, even in the absence of a glass envelope (whose purpose is only to exclude air, to prevent the filament oxidising).

At low-ish (e.g. mains) voltages an arc won't start spontaneously over more than about 0.5 mm - the resistance of dry air is too high for an appreciable current to flow. But if you gradually open a contact that has a high current flowing through it, the initial tiny arc provides the low-resistance path which can grow to a few millimeters if the current is high enough.

The arc of a spark plug is colored by the ionised metal of the plug - can be red for a simple car plug with iron electrodes or blue for silver or platinum plugs. Copper switches often show a green arc.
 
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Offline Thebox

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Re: Does electricity ''weaken'' when it is being ''stretched''?
« Reply #15 on: 19/12/2015 15:47:16 »
The resistance of the lamp filament (around 1000 ohm) is much lower than that of the air path to the ground (at least 1,000,000,000 ohms for dry air) so nearly all the current flows from the live to the neutral conductor, even in the absence of a glass envelope (whose purpose is only to exclude air, to prevent the filament oxidising).



Do you mean AC by this and the loop system of AC from Tesla?

To confirm my understanding, we take a Neutral copper coil, we evoke the atoms in the copper coil to become slightly excited by using a magnetic force, this creates electricity, the electricity then travels along a wire to an element , where it is converted into heat and light, which is released into the atmosphere, and ''any'' electrical charge released is instantly neutralised by space?


« Last Edit: 19/12/2015 15:55:24 by Thebox »
 

Offline evan_au

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Re: Does electricity ''weaken'' when it is being ''stretched''?
« Reply #16 on: 19/12/2015 21:13:05 »
Quote
Do you mean AC by this and the loop system of AC from Tesla?
Yes. Most light bulbs around the world are powered by AC, descendants of Tesla's inventions.

Quote
''any'' electrical charge released is instantly neutralised by space?
In Tesla's system, the electrical charge (electrons) remain in the wire, and move backwards and forwards by less than 1 mm under the influence of the AC voltage from the generator. Any segment of wire remains almost exactly electrically neutral.

At 110V/240V AC, there is almost no arcing (especially if the wire has plastic insulation), so there is almost no "charge released".

At 100,000V AC or more (such as in long-distance high voltage transmission lines), there is some amount of corona discharge, where electrons will jump out of the bare wires into the air, and then, when the voltage reverses, they will jump back into the wire. I would say that the "charge released" is neutralized by the wire when it reverses polarity just milliseconds later.

Corona discharge is an undesirable loss of power, which is mitigated by rounding off all sharp points on the transmission lines.
See: http://en.wikipedia.org/wiki/Corona_discharge
 

Offline Thebox

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Re: Does electricity ''weaken'' when it is being ''stretched''?
« Reply #17 on: 20/12/2015 12:34:39 »
Quote
Do you mean AC by this and the loop system of AC from Tesla?
Yes. Most light bulbs around the world are powered by AC, descendants of Tesla's inventions.

Quote
''any'' electrical charge released is instantly neutralised by space?
In Tesla's system, the electrical charge (electrons) remain in the wire, and move backwards and forwards by less than 1 mm under the influence of the AC voltage from the generator. Any segment of wire remains almost exactly electrically neutral.

At 110V/240V AC, there is almost no arcing (especially if the wire has plastic insulation), so there is almost no "charge released".

At 100,000V AC or more (such as in long-distance high voltage transmission lines), there is some amount of corona discharge, where electrons will jump out of the bare wires into the air, and then, when the voltage reverses, they will jump back into the wire. I would say that the "charge released" is neutralized by the wire when it reverses polarity just milliseconds later.

Corona discharge is an undesirable loss of power, which is mitigated by rounding off all sharp points on the transmission lines.
See: http://en.wikipedia.org/wiki/Corona_discharge

Thank you Evan and Alan.

Corona discharge, is this the same thing as after  400 miles ''up''?
 

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Re: Does electricity ''weaken'' when it is being ''stretched''?
« Reply #17 on: 20/12/2015 12:34:39 »

 

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